Mediator-Assisted Laccase-Catalyzed Oxidation of 4-Hydroxybiphenyl

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I. Bratkovskaya^1*, R. Ivanec², and J. Kulys^1,2

¹Institute of Biochemistry, Mokslininku 12, Vilnius LT-08662, Lithuania; fax: (8-370) 5272-9196; E-mail: bratkovskaja@bchi.lt

²Department of Chemistry and Bioengineering, Vilnius Gediminas Technical University, Sauletekio Av. 11, Vilnius LT-10223, Lithuania

^* To whom correspondence should be addressed.

Received September 30, 2005; Revision received October 23, 2005

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The kinetics of oxidation of 4-hydroxybiphenyl (4-HBP) catalyzed by laccase from Polyporus pinsitus was studied in the presence of methyl syringate (MS), which acts as an electron-transfer mediator. Measurements were performed in 0.05 M acetate buffer, pH 5.5, in the presence of 4-HBP, MS, and laccase. It is shown that the oxidation rate of the lowly reactive substrate 4-HBP significantly increases during synergistic action of the highly reactive substrate MS. Bimolecular kinetic constants of interaction between the oxidized form of laccase and MS, the former and 4-HBP, and the oxidized form of MS and 4-HBP were calculated. A kinetic scheme of the synergistic substrate action is suggested; based on this scheme, the dependence of the initial rate on reagent concentration is derived. Analyzing experimental data, we obtained kinetic constants close to those obtained by modeling the processes.

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KEY WORDS: 4-hydroxybiphenyl, laccase, methyl syringate, synergistic mechanism, kinetic constants

DOI: 10.1134/S0006297906050130

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